1. Field of the Invention
The present invention is directed to a hydrodynamic clutch arrangement, particularly a torque converter or fluid coupling, including a housing arrangement, a turbine wheel provided in the housing arrangement, and a lockup clutch arrangement by which a torque transmitting connection can be produced selectively between the turbine wheel and the housing arrangement. The lockup clutch arrangement includes at least two friction members which are rotatable with one of the housing arrangement and turbine wheel, at least one counter-friction member which is rotatable with the other of the housing arrangement and turbine wheel being interposed between two friction members.
2. Description of the Related Art
U.S. Pat. No. 6,293,380 discloses a hydrodynamic clutch arrangement in the form of a hydrodynamic torque converter. In this hydrodynamic torque converter, two friction members in the form of plates similar to friction disks are coupled with the turbine wheel for common rotation. These two plates lie between a clutch piston and an area of the housing arrangement. Friction surfaces with which corresponding friction surfaces at the two plates can be brought into contact are provided at the clutch piston and also at this area of the housing arrangement. Further, as an additional counter-friction member coupled with the housing arrangement for common rotation, a friction plate constructed in the manner of a ring disk is provided between the two friction members which are constructed as plates. This friction plate is pressed between the two plate-like friction members when the clutch piston is displaced. Friction facings are provided at the two friction members or plates at both sides, so that these friction facings can enter into frictional contact with the clutch piston or housing arrangement on the one hand and with the counter-friction member constructed as a ring disk on the other hand. Ultimately, this means that, in the area the friction members, the friction surface regions provided in this area are formed by surface regions of the friction facings, while metal surfaces form the friction surface regions in the area of the counter-friction members, i.e., the clutch piston, the structural component part which is constructed in the manner of a ring disk and located between the two friction members, and the housing arrangement.
The basic problem in a hydrodynamic clutch arrangement constructed in this way is that a comparatively large thermal load occurs in case of friction heat occurring in slip operation of the lockup clutch arrangement, particularly in the counter-friction element which is constructed in the manner of a ring disk and is located between the two plate-like friction elements. This is due to the fact that, first, this friction acts upon this structural component part over a large portion of its surface, so that there is only poor conduction of heat away from this structural component part. Also, its dimensions, particularly its thickness, are appreciably smaller, for example, than the clutch piston or housing arrangement in the area acted upon by friction, so that heat distribution in a larger volume area is also not possible in this case. Due to the nonuniform heating of the components or component areas in question during friction operation, local overheating can occur, so that damage to or failure of the entire lockup clutch arrangement can be caused in this overheated area in spite of the fact that other areas are not thermally overloaded.
U.S. Pat. No. 5,211,270 discloses a hydrodynamic clutch arrangement with a lockup clutch arrangement in which a counter-friction element which is constructed in the manner of a ring disk is connected with the housing arrangement so as to be rotatable. This counter-friction element constructed as a ring disk is located between a friction element which is constructed in the manner of a plate and a clutch piston which, in this case, is to be considered as an additional friction element which is rotatable in common with the plate-like friction element. In this arrangement also, the above-mentioned problem of local overheating due to comparatively poor capacity to dissipate heat can arise in the counter-friction element which is constructed as a ring disk and which is not provided with friction facings.
DE 198 26 351 discloses a hydrodynamic clutch arrangement in the form of a hydrodynamic torque converter in which the clutch piston as well as an abutment element are connected with the housing arrangement so as to be rotatable. Two plate-shaped friction members which have friction facings and are coupled with the turbine wheel for common rotation are located between these two elements. A counter-friction member which is constructed as a ring disk is located between these two friction members and, together with the abutment element and the clutch piston and another counter-friction member which is constructed as a ring disk and directly adjoins the clutch piston, is rotatable with the housing arrangement. In this arrangement, particularly in the region of the counter-friction member which is constructed as a ring disk and is interposed between the two friction members, there is a risk of local overheating due to the comparatively poor heat dissipation from this region.
It is the object of the present invention to further develop a hydrodynamic clutch arrangement of the type described above in such a way that the risk of local overheating due to heat generated in the region of the lockup clutch arrangement can be reduced or eliminated.
According to the present invention, this object is met by a hydrodynamic clutch arrangement, particularly a torque converter or fluid coupling, including a housing arrangement, a turbine wheel provided in the housing arrangement, and a lockup clutch arrangement by which a torque transmitting connection can be produced selectively between the turbine wheel and the housing arrangement. The lockup clutch arrangement includes at least two friction members which are rotatable with one of the housing arrangement and turbine wheel, at least one counter-friction member which is rotatable with the other of the housing arrangement and turbine wheel and which is interposed between two friction members. A first friction facing in at least one of the friction members at its first side faces the at least one counter-friction member. This at least one of the friction members can be brought into frictional interaction, via a second friction facing, with another counter-friction member on its second side located opposite the first side.
According to the invention, it is further provided that the first friction facing has a larger friction surface region than the second friction facing.
In a construction of this kind, it is ensured that a friction surface which is increased relative to other friction surface regions involved in friction is provided in the region of the at least one counter-friction member, so that heat concentrated on a smaller surface region or volume area can be prevented and the heat generated by friction can be distributed in an improved manner.
Further, in a construction of the type mentioned above, the second friction facing can be provided at the at least one of the at least two friction members.
The additional counter-friction member can comprise, for example, the housing arrangement, but can also or additionally comprise a pressing element of the lockup clutch arrangement.
In a construction of this type, a particularly advantageous operation can be achieved when the housing arrangement, the pressing element and the at least one counter-friction member are coupled with one another so as to rotate in common.
In this case, the at least two friction members are then preferably coupled with the turbine wheel for common rotation.
According to another advantageous feature of the present invention, the above-stated object is met by a hydrodynamic clutch arrangement, particularly a torque converter or fluid coupling, comprising a housing arrangement, a turbine wheel provided in the housing arrangement, and a lockup clutch arrangement by which a torque transmitting connection can be produced selectively between the turbine wheel and the housing arrangement. The lockup clutch arrangement includes at least two friction members which are rotatable with one of the housing arrangement and turbine wheel, at least one counter-friction member which is rotatable with the other of the housing arrangement and turbine wheel being interposed between two friction members.
According to the invention, a friction facing is provided on at least one side of the at least one counter-friction member for frictional interaction with the friction member located opposite to this side.
In a construction of the type mentioned above, the frictional load on the at least one counter-friction member can be reduced on at least one side of this at least one counter-friction member by providing a friction facing at this structural component part. However, a friction facing can preferably be provided at both sides of the at least one counter-friction member. In this way, excessive thermal loading of the at least one counter-friction member is extensively eliminated on both axial sides.
In such a construction of the hydrodynamic clutch arrangement according to the invention, a friction facing is preferably provided on at least one of the at least two friction members on the side of the same remote of the at least one counter-friction facing, wherein the at least one of the at least two friction members can be brought into frictional interaction with another counter-friction member by means of this friction facing. Alternatively, it is also possible that at least one of the at least two friction members can be brought into frictional interaction with another counter-friction member at its side remote of the at least one counter-friction member, and that a friction facing is provided at the other counter-friction member.
The additional counter-friction member can comprise, for example, the housing arrangement, but can also comprise a pressing element of the lockup clutch arrangement.
In this case, also, it is advantageous when the housing arrangement, the pressing element and the at least one counter-friction member are coupled with one another for common rotation. The at least two friction members are then advantageously coupled with the turbine wheel for common rotation.
According to another advantageous feature of the present invention, it can be provided further that at least one of the at least two friction members has a base body which has a greater thickness than a base body of the at least one counter-friction member.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.